1. Field of the Invention
The present invention relates to a disk device for recording or reproducing data on or from a disk-like recording medium like an optical disk and a control method for the disk drive. In particular, the present invention relates to the disk device which is suitable to be loaded in an information recording apparatus arranged to select a recording method according to each of recording formats and record information (often referred to as “data”) like a moving picture and voice on a recording medium and the control method for the disk device.
2. Description of the Related Art
A recordable optical disk is mainly used as an archive. Hence, unlike a magnetic information recording device like a harddisk drive, as to the recordable optical disk, attention has been focused on a recording capacity rather than a speed of access to recorded information or a speed of rewriting recorded information. As such, in general, the harddisk drive is constructed to record information as keeping rotation of a magnetic disk located in the drive at a constant angular velocity (CAV), while the recordable optical disk is constructed to record information as keeping the linear velocity on the disk circumference constant (that is, keeping the constant linear velocity (CLV) of the disk) for the purpose of enhancing the recording capacity of each disk.
In general, the recordable optical disk includes tracks spirally formed from the inner periphery to the outer periphery of the disk. When information is recorded on the recordable optical disk, marks are formed along the tracks through the effect of heat, for example. By making the length of one information recording unit provided when information is recorded on a track on the inner periphery of the optical disk equal to the length thereof provided when information is recorded on a track on the outer periphery of the optical disk (keeping the constant recording line density in both cases) in the track direction, it is possible to obtain more recording capacity of information to be recorded on one optical disk as compared with the recording format used in the magnetic disk located in the harddisk drive. The recording format used in the magnetic disk of the harddisk drive has as one information recording unit an arc length provided when an angle to an arc becomes constant. The length of one information recording unit is made variable according to the radial location of the disk. That is, the recording density is made lower toward the outer periphery.
Recently, a rewritable and recordable optical disk is generally a phase-change optical disk if the disk has a large capacity. This optical disk is constructed by forming amorphous marks on a crystalline area served as a recording layer of the optical disk through the use of heat of the condensed, or focused laser beam and then obtaining information as the corresponding signal through a difference of reflectivity between the amorphous portion and the crystalline portion. Since the marks are formed by heat, it is necessary to radiate the laser in consideration of heat conduction and diffraction on the disk. For recording a mark of a desired length on the disk, it is necessary to control a luminous intensity or a pulse luminous interval of the laser beam. (Hereafter, this kind of control about laser is called write strategy.) Hence, when information is recorded on the optical disk in such a recording format as keeping respective information recording units the same as each other independently of the radial location, by controlling rotation of the optical disk at the CLV, it is principally possible to use the same write strategy independently of the radial location. Hereafter, the operation of recording information as controlling rotation of the optical disk at the CLV in such a recording format as keeping the recording line density constant is called CLV recording.
For the CLV recording, the angular velocity of the optical disk is varied depending upon where of a radial location on the optical disk an objective lens for condensing, or focusing a laser beam on the surface of the optical disk is located. That is, when the objective lens is located on the outer periphery of the optical disk for recording information on the outer peripheral track of the optical disk, the angular velocity of the optical disk is less than that provided when the objective lens is located on the inner periphery. Therefore, when the objective lens is greatly moved from the inner periphery to the outer periphery or vice versa, it is necessary to control rotation of the optical disk so that the angular velocity of the optical disk is made to be a proper value and then to record information on the optical disk after the angular velocity thereof becomes the proper value.
In consideration of these matters, for example, JP-A-8-22676 discloses the disk reproducing apparatus which is arranged to control rotation of an optical disk at the CLV in the normal reproduction of data or at the CAV when accessing the disk from the inner periphery to the outer periphery or vice versa, for enhancing an access speed in reproducing a reproduction-dedicated disk on which information is recorded in such a recording format as keeping a recording line density constant.